JP2023006295A - Communication device, communication control method, and communication control program - Google Patents

Abstract

To provide a novel mechanism for maintaining stability in redundant networks.SOLUTION: A communication device includes a communication unit connected to a network configured such that frames circulate around. At least some pathways in the network are made redundant. One or a plurality of devices are connected to the network. The communication device includes: a gathering unit for gathering statistical information pertaining to the frames being delivered through the network; a connection management unit for transmitting a command to two devices to thereby logically disconnect a segment between the two devices; and an identification unit for identifying a segment included in the network in which a hindrance has occurred, the segment being identified on the basis of a change in statistical information when the segment is logically disconnected.SELECTED DRAWING: Figure 1

Description

The present invention relates to a communication device connected to a network, a communication control method in the communication device, and a communication control program for realizing the communication control method in the communication device.

For example, in a network conforming to EtherCAT (registered trademark), a communication frame (hereinafter also simply referred to as "frame") transmitted by a communication master (hereinafter also simply referred to as "master") is transmitted to all communication slaves (hereinafter simply referred to as (also called "slave"), and then return to the master. Normally, if a part of the route for circulating frames is cut, the frames cannot be transmitted between all the slaves.

Networks with redundant frame transmission paths have also been put to practical use in order to increase the resistance to such network failures. For convenience of explanation, a network with redundant paths is called a "redundant network" or a "ring configuration", and a network without redundant paths is called a "non-redundant network" or a "non-ring configuration". Also called

On the other hand, techniques and methods have been proposed for detecting faults occurring in networks.
For example, Japanese Patent Laying-Open No. 2008-244714 (Patent Document 1) discloses a line testing apparatus and a line testing method capable of executing an out-of-service line test without causing communication interruption of the main signal. Japanese Patent Laying-Open No. 11-112539 (Patent Document 2) discloses a technique for preventing stoppage of the communication function of the entire network even if a failure occurs in some elements of the ring network. Japanese Patent Laying-Open No. 64-16145 (Patent Document 3) discloses a network configuration control method suitable for quickly recovering from an abnormality in a communication function.

JP 2008-244714 A JP-A-11-112539 JP-A-64-16145

As described above, a redundant network has the advantage of being able to continue frame transmission even in the event of a permanent failure such as a disconnection. There are also things. Temporary failures include, for example, the loss of frames due to intermittent noise from devices close to the network. When such a situation occurs, the stability of frame transmission is degraded. In addition, it is assumed that the frames cannot be transmitted stably due to the deterioration of parts.

An object of one aspect of the present invention is to provide a new mechanism for maintaining stability in a redundant network.

A communication apparatus according to an embodiment of the present invention includes a communication unit connected to a network configured to allow frames to circulate. At least some routes in the network are redundant. One or more devices are connected to the network. The communication device includes a collection unit that collects statistical information about frames transmitted over the network, and a connection management unit that logically disconnects the section between the two devices by sending a command to the two devices. and an identification unit that identifies a section in which a fault has occurred based on changes in statistical information when sections included in the network are logically disconnected.

According to this configuration, when a section between two devices is logically disconnected and a fault occurs in the section, the statistical information may change. Based on such changes in statistical information, it is possible to reliably identify the section in which the fault has occurred. By specifying the section in which the fault occurs, the influence of the fault can be removed more easily.

The connection management unit may maintain a state in which the faulty section is separated from the network. According to this configuration, it is possible to eliminate the influence of the faulty section.

The connection management unit may isolate the faulty section from the network in accordance with the user's operation. According to this configuration, for example, when failures occur in a plurality of sections, the user can determine which section should be preferentially separated.

The statistical information may include an error rate indicating the ratio of the number of lost frames and frames with errors to the number of frames transmitted from the communication device. With this configuration, it is possible to quantitatively evaluate errors that may occur in frames transmitted over the network.

The identifying unit may determine the possibility of a faulty section based on the degree to which the error rate of each logically connected section is suppressed. According to this configuration, when failures occur in a plurality of sections, it is possible to easily identify failures that may have a greater impact.

The identifying unit may start the process of identifying the faulty section when the statistical information satisfies a predetermined condition. According to this configuration, unless some kind of failure occurs, the process of identifying the section in which the failure occurs is not started, so the processing load on the communication device can be reduced.

The connection management unit sequentially selects two adjacent devices, transmits a port close command to the selected two devices, and then transmits a port open command to the selected two devices. You may make it transmit. According to this configuration, two devices can be arbitrarily selected in sequence, and the interval between each selected two devices can be evaluated in sequence.

The communication device further includes a notification unit for notifying the outside of the section in which the failure has occurred. According to this configuration, it is possible to inform the user or the like of the section in which the failure occurs.

According to another embodiment of the present invention, there is provided a communication control method executed by a communication device connected to a network configured to loop frames. At least some routes in the network are redundant. One or more devices are connected to the network. A communication control method includes the steps of collecting statistical information about frames transmitted over a network, sending a command to two devices to logically disconnect a section between the two devices, and identifying a section in which a fault occurs based on changes in statistical information when sections included in the network are logically disconnected.

According to yet another embodiment of the present invention, there is provided a communication control program executed by a computer connected to a network configured to loop frames. At least some routes in the network are redundant. One or more devices are connected to the network. The communication control program instructs the computer to collect statistical information about frames transmitted over the network, and to send a command to two devices to logically disconnect the section between the two devices. and identifying a section in which a fault has occurred based on changes in statistical information when sections included in the network are logically disconnected.

According to one embodiment of the present invention, stability can be maintained in a redundant network.

1 is a schematic diagram showing a network configuration example of a communication system according to the present embodiment; FIG. 2 is a schematic diagram showing a hardware configuration example of a PLC of the communication system according to the present embodiment; FIG. 2 is a schematic diagram showing a hardware configuration example of a device of the communication system according to the present embodiment; FIG. 3 is a schematic diagram showing a hardware configuration example of a relay device of the communication system according to the present embodiment; FIG. FIG. 4 is a diagram for explaining an example of processing for identifying and isolating a failure location in the communication system according to the present embodiment; FIG. 4 is a flow chart showing a processing procedure for identifying and isolating a failure location in the communication system according to the present embodiment; FIG. 4 is a diagram for explaining a processing example when there is one failure location in the communication system according to the present embodiment; FIG. 4 is a diagram for explaining a processing example when there are two failure locations in the communication system according to the present embodiment; FIG. 4 is a diagram for explaining a processing example when a failure occurs in a non-redundant path in the communication system according to the present embodiment; 2 is a schematic diagram showing a hardware configuration example of a support device of the communication system according to the present embodiment; FIG. FIG. 4 is a schematic diagram showing an example of a user interface screen provided by a support device of the communication system according to the present embodiment; FIG. 4 is a schematic diagram showing another example of a user interface screen provided by the support device of the communication system according to the present embodiment; FIG. 9 is a schematic diagram showing yet another example of a user interface screen provided by the support device of the communication system according to the present embodiment; 1 is a diagram showing an example of a redundant network that can be employed in a communication system according to this embodiment; FIG.

Embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are given the same reference numerals, and the description thereof will not be repeated.

<A. Application example>
First, an example of a scene to which the present invention is applied will be described.

FIG. 1 is a schematic diagram showing a network configuration example of a communication system 1 according to this embodiment. 1A and 1B, a communication system 1 includes a communication device (PLC 100 as an example) functioning as a communication master (master) and an input/output device functioning as a communication slave (slave). etc. (hereinafter also collectively referred to as “functional device 200”) and relay device 300 . Also, the functional device 200 and relay device 300 may be collectively referred to as "device" or "slave device". Both masters and devices are connected to the network.

In the following description, a PLC (Programmable Logic Controller) that executes arbitrary control calculations is assumed as an example of a communication device, but the present invention is not limited to PLCs and can be applied to any device that can function as a master. .

The PLC 100 has a port 151 for transmitting and receiving frames. Each of functional devices 200-1 to 200-5 has a first port 251 and a second port 252 for transmitting and receiving frames.

In each functional device 200, the first port 251 is normally used as a frame input port (IN port), and the second port 252 is normally used as a frame output port (OUT port). However, if a part of the path constituting the network is cut off, each of the first port 251 and the second port 252 is a port (IN port) to which frames are input and/or a frame is output. Used as a port (OUT port).

The relay device 300 has a first port 351, a second port 352 and a third port 353 for transmitting and receiving frames. When relay device 300 receives a frame at one port, relay device 300 transmits the received frame from another port determined according to a predetermined rule. In the example shown in FIG. 1A, even if a cyclic rule such as the first port 351→the second port 352→the third port 353→the first port 351→ . good.

In normal frame transmission, a frame transmitted from port 151 of PLC 100 is transmitted through cable 20, first port 351 of relay device 300, second port 352 of relay device 300, cable 21, first port 351 of functional device 200-1. port 251, second port 252 of functional device 200-1, cable 22, first port 251 of functional device 200-2, second port 252 of functional device 200-2, cable 23, first port 252 of functional device 200-3 Port 251, second port 252 of functional device 200-3, cable 24, first port 251 of functional device 200-4, second port 252 of functional device 200-4, cable 25, first port 252 of functional device 200-5 The port 251 , the second port 252 of the functional device 200 - 5 , the cable 26 , the third port 353 of the relay device 300 , and the cable 20 are cycled in order, and then returned to the port 151 of the PLC 100 .

In the network shown in FIG. 1, the route from relay device 300 to terminal functional device 200-5 includes the routes of cables 21 to 25 and the route of cable . That is, the network has two routes, and at least some of the routes are made redundant.

The PLC 100 includes a collection module 50, a connection management module 60, and an identification module 70 as functional configurations.

A collection module 50 collects statistical information about frames transmitted over the network.

The connection management module 60 manages disconnection/connection of any section of the network by transmitting any command to the devices (functional device 200 and relay device 300) connected to the network. Typically, the connection management module 60 sends commands to logically close ports to two adjacent devices, thereby logically disconnecting the section between the two devices. Also, the connection management module 60 logically connects the section between the two devices by sending a command to logically open the port to the two adjacent devices.

The identification module 70 identifies a section in which a fault has occurred based on changes in statistical information when sections included in the network are logically disconnected.

As used herein, "failure" is a concept encompassing any event that adversely affects frame transmission. The "failure" includes, for example, external noise that interferes with frame transmission, degradation of components, disconnection or breakage of cables, and the like.

A typical example of identifying a faulty section by the identifying module 70 will be described below.

As shown in FIG. 1A, it is assumed that a failure occurs between functional devices 200-2 and 200-3. In this situation, frame transmission on the network is affected, and the statistical information collected by the collection module 50 will include features that indicate that something is wrong with frame transmission.

Assume that the connection management module 60 logically disconnects the section between the functional device 200-2 and the functional device 200-3, as shown in FIG. 1B. Then, the frame is folded back at functional device 200-2 and functional device 200-3, respectively, so that it does not pass between functional device 200-2 and functional device 200-3 in which the fault has occurred. As a result, the frame transmission is not affected, and the statistical information collected by the collection module 50 will have suppressed characteristics indicating that the frame transmission is in some way abnormal.

The connection management module 60 sequentially switches the section to be logically disconnected, and the identification module 70 identifies the section in which the failure is occurring based on the change in statistical information for each logically disconnected section.

The configuration, processing, functions, etc. for realizing such a mechanism will be described in detail below.
<B. Hardware configuration example>
Next, a hardware configuration example of each device configuring communication system 1 according to the present embodiment will be described.

(b1: communication device (PLC 100))
FIG. 2 is a schematic diagram showing a hardware configuration example of PLC 100 of communication system 1 according to the present embodiment. Referring to FIG. 2, PLC 100 includes processor 102, main memory 104, storage 110, field network controller 112, and local bus controller 114 as main hardware components. These hardware components are electrically connected via internal bus 118 .

The processor 102 corresponds to an arithmetic processing unit that executes control arithmetic, and includes a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and the like. Specifically, the processor 102 reads out the program stored in the storage 110, develops it in the main memory 104, and executes it, thereby realizing control calculation according to the control target and various processes described later. do.

The main memory 104 is composed of a volatile storage device such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory). The storage 110 is configured by, for example, a non-volatile storage device such as SSD (Solid State Drive) or HDD (Hard Disk Drive).

The storage 110 stores a system program 1102 for realizing basic functions, a user program 1104 created according to the object to be controlled, and the like. The system program 1102 implements basic functions in the PLC 100 and can be regarded as at least part of the communication control program.

Typically, system program 1102 includes instructions for implementing connection management module 60 and specific module 70 (FIG. 1).

The field network controller 112 corresponds to a communication unit, and is connected to a network configured so that frames circulate. More specifically, the field network controller 112 has a port 151 and is in charge of frame transmission/reception processing. The field network controller 112 of the PLC 100 has a network management module 1122 for acting as a master. The network management module 1122 collects statistical information about frames transmitted over the network. That is, network management module 1122 includes collection module 50 (FIG. 1). Additionally, the field network controller 112 may have a synchronization counter for periodically transmitting and receiving frames.

Local bus controller 114 is electrically coupled to one or more functional units 116 via internal bus 118 . The functional unit 116 includes functions for exchanging various signals with the controlled object. The functional unit 116 has, for example, a DI (Digital Input) function for receiving a digital signal from the controlled object, a DO (Digital Output) function for outputting a digital signal to the controlled object, and an AI (Analog Signal) function for receiving an analog signal from the controlled object. input) function and an AO (Analog Output) function of outputting an analog signal to a controlled object. Furthermore, the functional unit 116 may include a controller implementing special functions such as PID (Proportional Integral Derivative) control and motion control.

FIG. 2 shows a configuration example in which necessary functions are provided by the processor 102 executing a program. (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array), etc.). Alternatively, the main part of the PLC 100 may be realized using hardware conforming to a general-purpose architecture (for example, an industrial personal computer based on a general-purpose personal computer). In this case, virtualization technology may be used to execute a plurality of OSs (Operating Systems) for different purposes in parallel, and necessary applications may be executed on each OS.

Also, each of the collection module 50, the connection management module 60, and the identification module 70 shown in FIG. 1 may be implemented in any way.

Furthermore, a configuration in which functions such as a display device and a support device are integrated into the PLC 100 may be adopted.

(b2: functional device 200)
FIG. 3 is a schematic diagram showing a hardware configuration example of functional device 200 of communication system 1 according to the present embodiment. Referring to FIG. 3, functional device 200 includes a control circuit 206, a field network controller 212, and a functional module 220 as main hardware components.

The control circuit 206 is an arithmetic processing unit that mainly executes processing in the functional device 200 . Control circuitry 206 typically includes a processor 202 , main memory 204 , and storage 210 . The processor 202 is composed of a CPU, a GPU, and the like. The main memory 204 is composed of a volatile memory device such as DRAM and SRAM. The storage 210 is configured by, for example, a non-volatile storage device such as an SSD. Note that a ROM (Read Only Memory) may be employed as the storage 210 .

Note that the control circuit 206 may be implemented using a dedicated hardware circuit (eg, ASIC or FPGA).

The field network controller 212 has a first port 251 and a second port 252 and is in charge of frame transmission/reception processing. The field network controller 212 of the functional device 200 functions as a communication slave (slave). Note that the field network controller 212 may have a synchronous counter for periodically transmitting and receiving frames.

The functional module 220, like the functional unit 116 shown in FIG. 2, takes charge of processing such as exchanging various signals with the controlled object.

(b3: relay device 300)
FIG. 4 is a schematic diagram showing a hardware configuration example of relay device 300 of communication system 1 according to the present embodiment. Referring to FIG. 4, relay device 300 includes a control circuit 306 and a field network interface 312 as main hardware components.

The control circuit 306 is an arithmetic processing unit that mainly executes frame transmission processing in the relay device 300 . Control circuitry 306 typically includes a processor 302 , main memory 304 , and storage 310 . The processor 302 is composed of a CPU, GPU, or the like. The main memory 304 is composed of a volatile storage device such as DRAM and SRAM. The storage 310 is configured by, for example, a non-volatile storage device such as an SSD. Note that a ROM may be employed as the storage 310 .

Note that the control circuit 306 may be implemented using a dedicated hardware circuit (for example, ASIC or FPGA).

The field network interface 312 has a first port 351, a second port 352 and a third port 353 for transmitting and receiving frames. Note that the relay device 300 is also treated as one slave when viewed from the master.

<C. Identification and Isolation of Fault Location>
Next, processing for identifying and isolating a failure location in communication system 1 according to the present embodiment will be described. Communication system 1 according to the present embodiment identifies (or presume.

More specifically, the PLC 100 logically and sequentially disconnects each section of the network, and identifies the failure location from changes in statistical information that occur according to the disconnected sections.

Since the communication system 1 employs a redundant network (ring configuration), frame transmission continues even if a part of the path configuring the network is logically disconnected.

Here, the statistical information is the result of summarizing the states of frames transmitted over a network over a predetermined period, and includes information such as loss of frames and generation of error frames. More specifically, frame loss means a state in which a frame transmitted from PLC 100 does not return to PLC 100 within a predetermined time (timeout). Also, occurrence of an error frame means a state in which data in a frame is corrupted based on error detection information (check bit, parity bit, etc.) included in the frame. Hereinafter, the frequency of occurrence of some abnormality included in the statistical information is also collectively referred to as "error occurrence rate". The error rate corresponds to the number of times errors occur per unit time. More specifically, the error rate indicates the ratio of the number of lost frames and error-generated frames to the number of frames transmitted from the PLC 100 .

PLC 100 can send commands to logically open/close ports to arbitrary devices (functional device 200 and relay device 300). On the other hand, each device logically opens/closes the designated port according to the command from the PLC 100 . By logically closing the port, it becomes impossible to transmit or receive frames through the target port, which is essentially the same as the target port being physically disconnected. Conversely, logically opening a port is effectively the same as having the target port physically connected.

As a specific processing order, first, the PLC 100 detects that some kind of failure has occurred by increasing the error occurrence rate of the statistical information 160 . By transmitting a command to the functional device 200, the PLC 100 sequentially disconnects each section of the network, and determines whether or not the disconnected section is a failure location based on changes in the statistical information 160 in each state. to judge whether Finally, the PLC 100 separates the section corresponding to the specified failure location.

FIG. 5 is a diagram for explaining an example of fault location identification and isolation processing in communication system 1 according to the present embodiment. FIG. 5 shows an example in which a failure occurs between the functional devices 200-2 and 200-3.

Referring to FIG. 5A, first, PLC 100 disconnects the section between relay device 300 and functional device 200-1. More specifically, PLC 100 transmits a command to close second port 352 of relay device 300 and a command to close first port 251 of functional device 200-1. Then, no frame is transmitted between the second port 352 of the relay device 300 and the first port 251 of the functional device 200-1.

In this state, in relay device 300 , frames received at first port 351 are transmitted from third port 353 instead of second port 352 . Further, when the functional device 200 - 1 receives the frame at the second port 252 , it transmits the processed frame from the second port 252 . That is, the frame is folded back at the second port 252 of the functional device 200-1. By changing the transmission route of the frame in this way, the transmission of the frame is continued.

The PLC 100 determines whether or not the error rate of the statistical information 160 continues to be relatively high while the section is cut. In the state of FIG. 5(A), the disconnected section does not include the failure point, so the state of relatively high error occurrence rate continues. Therefore, the PLC 100 determines that the failure location is in another section. Then, the PLC 100 reconnects the disconnected section. More specifically, PLC 100 transmits a command to open second port 352 of relay device 300 and a command to open first port 251 of functional device 200-1.

Referring to FIG. 5B, PLC 100 then disconnects the section between functional device 200-1 and functional device 200-2. More specifically, PLC 100 transmits a command to close second port 252 of functional device 200-1 and a command to close first port 251 of functional device 200-2. Then, no frame is transmitted between the second port 252 of the functional device 200-1 and the first port 251 of the functional device 200-2.

In this state, functional device 200 - 1 transmits the processed frame from first port 251 upon receiving a frame at first port 251 . That is, the frame is looped back at the first port 251 of the functional device 200-1. Similarly, when functional device 200 - 2 receives a frame at second port 252 , it transmits the processed frame from second port 252 . That is, the frame is folded back at the second port 252 of the functional device 200-2. By changing the transmission route of the frame in this way, the transmission of the frame is continued.

The PLC 100 determines whether or not the error rate of the statistical information 160 continues to be relatively high while the section is cut. In the state of FIG. 5(B), the disconnected section does not include the failure point, so the state of relatively high error occurrence rate continues. Therefore, the PLC 100 determines that the failure location is in another section. Then, the PLC 100 reconnects the disconnected section. More specifically, PLC 100 transmits a command to open second port 252 of functional device 200-1 and a command to open first port 251 of functional device 200-2.

Referring to FIG. 5(C), PLC 100 then disconnects the section between functional device 200-2 and functional device 200-3. More specifically, PLC 100 transmits a command to close second port 252 of functional device 200-2 and a command to close first port 251 of functional device 200-3. Then, no frame is transmitted between the second port 252 of the functional device 200-2 and the first port 251 of the functional device 200-3.

In this state, when the functional device 200 - 2 receives a frame at the first port 251 , it transmits the processed frame from the first port 251 . That is, the frame is looped back at the first port 251 of the functional device 200-2. Similarly, when functional device 200 - 3 receives a frame at second port 252 , it transmits the processed frame from second port 252 . That is, the frame is folded back at the second port 252 of the functional device 200-3. By changing the transmission route of the frame in this way, the transmission of the frame is continued.

The PLC 100 determines whether or not the error rate of the statistical information 160 continues to be relatively high while the section is cut. In the state of FIG. 5(C), the cut section includes the faulty location, so the error rate is suppressed. Therefore, the PLC 100 determines that there is a failure point in the currently connected section. Then, the PLC 100 maintains the target section in a disconnected state. In this state, the process of identifying the fault location and isolating the fault location is completed.

FIG. 6 is a flow chart showing a processing procedure for identifying and isolating a failure location in communication system 1 according to the present embodiment. Each step shown in FIG. 6 may be implemented by processor 102 of PLC 100 functioning as a master executing system program 1102 (an example of a communication control program).

Referring to FIG. 6, PLC 100 collects statistical information 160 about frames transmitted over the network. More specifically, the PLC 100 acquires the error rate of the statistical information 160 (step S2). Then, the PLC 100 determines whether or not the acquired error rate satisfies a predetermined failure occurrence criterion (step S4). Failure occurrence criteria include, for example, an error rate exceeding a predetermined threshold. If the acquired error rate does not satisfy the failure occurrence criteria (NO in step S4), the processes from step S2 onward are repeated.

If the obtained error rate satisfies the failure occurrence criteria (YES in step S4), PLC 100 determines that some kind of failure has occurred in the network (step S6). Then, the process of specifying and isolating the fault location as described below is started. In this way, the PLC 100 may start the process of identifying the faulty section when the statistical information 160 satisfies a predetermined condition.

The PLC 100 logically disconnects the section between the two devices by sending a command to the two devices. More specifically, the PLC 100 selects the target section from among the sections included in the network (step S8). Then, the PLC 100 transmits commands to close the two ports connected to the selected target section (step S10). A close command logically disconnects the target segment of the network.

Then, PLC100 acquires the error rate of the statistical information 160 (step S12). Then, the PLC 100 determines whether or not the acquired error occurrence rate satisfies a predetermined failure point identification criterion (step S14). The fault location identification criteria include, for example, that the error rate is equal to or less than a predetermined threshold. That is, the PLC 100 determines whether or not the error rate has been suppressed by cutting the target section.

If the acquired error rate satisfies the failure occurrence criteria (YES in step S14), the PLC 100 determines that a failure has occurred in the target section (step S16). The PLC 100 performs necessary notification processing and the like (step S18), and maintains the state in which the current target section is disconnected (step S20). In this way, the PLC 100 maintains a state in which the faulty section is separated from the network. Then the process ends.

On the other hand, if the acquired error rate does not satisfy the failure occurrence criteria (NO in step S14), the PLC 100 determines that no failure has occurred in the target section, and connects to the selected target section. A command to open each of the two ports identified is transmitted (step S22).

In this way, the PLC 100 identifies the faulty section based on the change in the statistical information 160 when the sections included in the network are logically disconnected. At this time, the PLC 100 sequentially selects two adjacent devices, transmits a command to close the port to the selected two devices, and then a command to open the port to the selected two devices. to send.

Subsequently, the PLC 100 determines whether or not all sections included in the network have been selected (step S24).

If all sections included in the network have not been selected (NO in step S24), PLC 100 selects a target section from unselected sections included in the network (step S26). Then, the processing from step S10 is repeated.

If all sections included in the network have been selected (YES in step S24), PLC 100 determines that the failure location cannot be uniquely identified (step S28). The PLC 100 executes processing for estimating the location of the failure as necessary (step S30). Then the process ends.

<D. Estimation of Failure Location>
Next, some examples of estimating the fault location will be described. Specifically, according to how the error rate changes for each section, the possibility of a fault location is estimated, and the sections to be separated are prioritized.

FIG. 7 is a diagram for explaining a processing example when there is one failure location in communication system 1 according to the present embodiment. As shown in FIG. 7A, assume an example where a failure occurs between the functional device 200-2 and the functional device 200-3.

As shown in FIG. 7B, it is assumed that the error rate (=number of error frames/number of transmitted frames), which is an example of the statistical information 160, is 10% before disconnecting the network section.

Note that the error rate is a value acquired in step S2 shown in FIG. It is calculated as the overall error rate (=number of error frames/number of frames transmitted (or number of frames received)). Note that the number of error frames includes frames lost during transmission in addition to frames in which some kind of error has occurred.

As described above, the PLC 100 identifies the fault location based on changes in the statistical information 160 while cutting each section. As shown in FIG. 7C, the statistical information 160 includes the error rate when each section is cut.

The error rate when each section is cut is the value acquired in step S12 shown in FIG. 6, and when each section is cut, the number of frames transmitted (or number) and the number of error frames, the error rate (=number of error frames/number of frames transmitted (or number of frames received)) when each section is cut is calculated.

The PLC 100 calculates a contribution rate as an effect of suppressing the error rate caused by cutting each section based on the change in the error rate when each section is cut. The contribution rate indicates the degree to which the error rate of each logically connected section is suppressed. More specifically, the contribution ratio means the ratio of the reduction amount of the error occurrence rate when cutting each section calculated based on the error occurrence rate before cutting. That is, the contribution rate is calculated as {(error rate before cutting)-(error rate when each section is cut)}/(error rate before cutting). Thus, the contribution rate is calculated based on the error rate of the entire network and the error rate when each section is cut.

In the example shown in FIG. 7C, the contribution rate is 100% when the section S3-S4 (between the functional device 200-2 and the functional device 200-3) is disconnected, and the contribution rate is 100% for other sections. Since the rate is 0%, the cutting target is uniquely determined between S3 and S4. That is, "1" is set as the priority only for S3-S4.

FIG. 8 is a diagram for explaining a processing example when there are two failure locations in communication system 1 according to the present embodiment. As shown in FIG. 8A, an example in which a failure occurs between functional device 200-2 and functional device 200-3 and between functional device 200-4 and functional device 200-5 is assumed. Suppose.

As shown in FIG. 8B, it is assumed that the error rate (=number of error frames/number of transmitted frames), which is an example of the statistical information 160, is 10% before disconnecting the network section.

In the example shown in FIG. 8C, the contribution rate is 70% when S3-S4 (between the functional device 200-2 and the functional device 200-3) is disconnected, and S5-S6 (between the functional device 200-4 and functional device 200-5) is 30%. Note that the contribution rate is 0% for other sections.

In such a state, priority is set in descending order of contribution rate. That is, "1" is set as the priority between S3 and S4, and "2" is set as the priority between S5 and S6.

Ultimately, the section between S3 and S4, which has a higher priority, is determined to be disconnected. However, it is also assumed that S5-S6, which has the next highest priority, is selected as a disconnection target.

In this way, the PLC 100 may determine the possibility of a fault occurring section based on the contribution rate indicating the degree to which the error rate of each logically connected section is suppressed. .

FIG. 9 is a diagram for explaining a processing example when a failure occurs in a non-redundant path in communication system 1 according to the present embodiment. As shown in FIG. 9A, an example is assumed in which a failure occurs between the PLC 100 and the relay device 300. FIG.

As shown in FIG. 9B, it is assumed that the error rate (=number of error frames/number of transmitted frames), which is an example of the statistical information 160, is 10% before disconnecting the network section.

In the example shown in FIG. 9C, the contribution rate is 0% regardless of which section is cut. Based on this result, the PLC 100 determines that there is no failure point in the cut section. Note that the section between the PLC 100 and the relay device 300 is not redundant and cannot be disconnected. Therefore, the PLC 100 notifies, for example, that some kind of failure has occurred in the non-redundant path.

As described above, the PLC 100 calculates the error rate when each section is disconnected, and among the calculated error rates, the section that has a high degree of influence on the error rate of the entire network can be the failure location. determined to have a high degree of potential for isolation from the network. At this time, the separation targets may be prioritized according to the degree of influence.

<E. Information provision to users>
Next, a configuration example in which communication system 1 according to the present embodiment provides information to users will be described.

(e1: support device)
Information provided by the communication system 1 may be provided to the user via a support device 400 connectable to the PLC 100 .

FIG. 10 is a schematic diagram showing a hardware configuration example of support device 400 of communication system 1 according to the present embodiment. Referring to FIG. 10, support device 400 is implemented, as an example, using hardware (for example, a general-purpose personal computer) conforming to a general-purpose architecture.

The support device 400 provides an integrated development environment that enables the setting of the PLC 100 and the functional device 200 of the communication system 1 and the creation of the user program 1104 executed by the PLC 100 in an integrated manner. Debugging and simulation may be possible in the integrated development environment.

Referring to FIG. 10, support device 400 includes, as main hardware components, processor 402, main memory 404, input unit 406, display unit 408, storage 410, communication controller 412, and optical drive 416. , and the USB controller 424 . These hardware components are electrically connected via internal bus 228 .

Processor 402 is composed of a CPU, a GPU, or the like, and implements the function of support device 400 by reading out a program stored in storage 410, developing it in main memory 404, and executing it.

The main memory 404 is composed of a volatile storage device such as DRAM and SRAM. The storage 410 is configured by, for example, a non-volatile storage device such as an HDD or SSD.

The storage 410 stores an OS 4102 for realizing basic functions, a development program 4104 for realizing an integrated development environment, and the like. The development program 4104 is executed by the processor 402 to provide an integrated development environment.

An input unit 406 includes a keyboard, a mouse, and the like, and receives user operations.
A display unit 408 includes a display, various indicators, and the like, and outputs processing results from the processor 402 and the like.

The communication controller 412 exchanges data with any information processing device via any upper network.

The optical drive 416 reads arbitrary data from a storage medium 418 (for example, an optical storage medium such as a DVD) that stores a computer-readable program non-transitory, and writes arbitrary data to the storage medium 418. can be done.

The USB controller 424 exchanges data with any information processing device via a USB connection.

A program stored therein may be read from a storage medium 418 that non-transitory stores a computer-readable program and installed in storage 410 or the like. Alternatively, various programs to be executed by the support device 400 may be installed by being downloaded from a server device or the like on the network. Also, the functions provided by support apparatus 400 according to the present embodiment may be realized by using some of the modules provided by OS 4102 .

Note that the support device 400 may be removed from the PLC 100 while the communication system 1 is in operation.

(e2: User interface example)
In communication system 1 according to the present embodiment, PLC 100 has a notification function for notifying the outside of information such as a section in which a failure has occurred. Information provided from the PLC 100 may be presented to the user via the support device 400 or the like. For example, the following information is assumed as the information provided to the user.

・Identified failure location ・Separated failure location ・If the failure location cannot be identified, a message indicating that a failure has occurred in a non-redundant route. 4 is a schematic diagram showing an example of a user interface screen provided by device 400. FIG.

Referring to FIG. 11(A), user interface screen 450 includes a network configuration diagram 452 showing the target network configuration. A network configuration diagram 452 shows the connection configuration of PLC 100 , functional device 200 and relay device 300 that configure communication system 1 . Among the nodes included in the network configuration diagram 452 , a section identified as a fault location is superimposed with a highlighting 454 . A section identified as a fault location by highlighting 454 is displayed in a manner different from that between other nodes. Since FIG. 11A shows an example in which two failure locations are specified, two highlighted displays 454 are superimposed.

The user interface screen 450 shown in FIG. 11A further includes a separated mark 456 indicating the separated section. Even if a plurality of fault locations are identified, only one separated mark 456 is displayed because normally one section is separated.

FIG. 11B shows a user interface screen 450 when the user separates the fault location from the network. Using the cursor 460 , the user selects a section to be separated from the section on which the highlight 454 is superimposed on the network configuration diagram 452 . Then, a dialog 458 for instructing separation is displayed, and the user can further select the displayed dialog 458 to separate the selected section from the network. In this way, the PLC 100 may separate the faulty section from the network according to the user's operation.

FIG. 12 is a schematic diagram showing another example of a user interface screen provided by support device 400 of communication system 1 according to the present embodiment. Referring to FIG. 12, user interface screen 450 displays the contribution rate of the fault location. More specifically, user interface screen 450 includes network diagram 452 . When the user points the failure location with the cursor 460, the contribution rate 462 of the target failure location is displayed. The user can refer to the contribution rate 462 for each fault location to determine which fault location to isolate.

FIG. 13 is a schematic diagram showing still another example of a user interface screen provided by support device 400 of communication system 1 according to the present embodiment. Referring to FIG. 13, user interface screen 470 includes contribution rates for each section.

By referring to the user interface screen 470 and referring to the contribution rate for each section, the user can more easily select which fault location to isolate.

(e3: form of information provision)
The provision of information as described above is not limited to the form using the user interface screen displayed on the support apparatus 400 as described above, and any form as described below is possible.

(1) Support Device As described above, the user interface screen displayed on the support device 400 may be used to display the identified fault location and related information.

Further, the support device 400 may read and display the values of the system definition variables (for example, flags indicating whether or not a failure has occurred or the location of the failure) managed by the PLC 100 .

Further, the support device 400 may read and display an event log (including, for example, messages such as details of failure occurrence) managed by the PLC 100 .

(2) HMI (Human Machine Interface)
An HMI that can communicate with the PLC 100 may be provided in the communication system 1 . The HMI, like the support device 400, may provide various information read from the PLC 100 by any method.

(3) User Program Various information may be provided by any method using dedicated instructions written in the user program 1104 executed by the PLC 100 . Dedicated instructions may include instructions for acquiring fault information, instructions for starting/stopping identification of fault locations, instructions for isolating/reconnecting fault locations, and the like.

By providing the user with the information described above, it is possible to prompt the user to generate a failure and to repair the failure location. Even in a redundant network, if some kind of failure occurs, the stability will decrease, so by repairing the failure point, the original stability can be secured earlier.

<F. Variation>
In addition to the exemplary embodiments described above, the following variations are possible. It should be noted that any one or more of the modifications shown below can be applied in appropriate combination.
(1) Conditions for Starting Failure Point Identification and Isolation Processing In the above-described embodiments, when the error rate satisfies a predetermined failure occurrence criterion, the failure point identification and isolation processing is started. be done. In this way, the PLC 100 may monitor the error rate and the number of error frames, and automatically start identifying and isolating the fault location when predetermined conditions are met.

Alternatively, the user may give a dedicated instruction to the PLC 100 via the support device 400, thereby automatically starting the process of identifying and isolating the failure location.

Alternatively, an arbitrary start condition including a dedicated instruction is described in the user program 1104, and the PLC 100 executes the user program 1104. When the described start condition is satisfied, the location of the failure is specified and The separation process may be started automatically.

Note that the failure occurrence criteria may also be arbitrarily set by the user. For example, by using an arbitrary threshold as a failure occurrence criterion, if the error occurrence rate is equal to or less than a predetermined threshold, it may not be regarded as a failure occurring in the network.
(2) Statistical Information As the statistical information, information from any point of view can be used.

For example, the frequency of anomalies occurring per unit time (for example, every second) may be used as statistical information, or the degree of anomalies relative to the number of unit frames (for example, every 1000 frames) may be used as statistical information. . Furthermore, temporal changes in the number of occurrences of anomalies (error counts) may be used as statistical information.

Also, the unit time and the number of unit frames used as statistical information may be arbitrarily set by the user.
(3) Separation and Recovery Although the processing example of maintaining the identified failure location in a separated state after identifying the failure location has been described, the user can arbitrarily select whether or not to isolate the failure location. good. In this case, for example, while notifying the user of information that enables the location of the failure to be identified, the location of the failure may be isolated only when an instruction for isolation is received from the user.

The instruction for separation from the user may be given to PLC 100 by the user operating support device 400, or may be given to PLC 100 using a dedicated command written in user program 1104 executed by PLC 100.

In addition, when the cause of the fault that occurred in the network is removed, the isolation of the section including the fault location may be released (restored) by an arbitrary method. For example, when the PLC 100 detects that a cable is physically disconnected and reconnected in a logically disconnected section, the PLC 100 may release the separation of the logically disconnected section. Alternatively, the user may operate the support device 400 to instruct the PLC 100 to reconnect the disconnected section.
(4) Execution entity of processing In the above description, an example in which the PLC 100 functioning as a master executes all processing has been described. may be executed in part or in whole.

The other device may be the support device 400 connected to the PLC 100 or any information processing device other than the support device 400 . Furthermore, the processing according to the present embodiment may be realized using computing resources on a so-called cloud.

<G. Redundant network>
In the above description, an example of a redundant network using the relay device 300 has been described, but the configuration is not limited to this and other configurations may be adopted.

FIG. 14 is a diagram showing an example of redundant networks that can be employed in communication system 1 according to the present embodiment.

FIG. 14A shows an example of a redundant network using relay devices 300 having three or more ports. The relay device 300 provides junction redundancy by having three or more ports. The redundant network shown in FIG. 14A includes relay devices 300 connected to the field network controller 112 (communication unit) of the PLC 100 and a plurality of functional devices 200 .

FIG. 14B shows an example of a redundant network using PLCs 100 having two or more ports 151 and 152. In FIG. The PLC 100 provides cable redundancy by having two or more ports. In the redundant network shown in FIG. 14B, the field network controller 112 (communication unit) of the PLC 100 has multiple ports connected to different functional devices 200 respectively.

Moreover, the relay device 300 shown in FIG. 14(A) and the PLC 100 shown in FIG. 14(B) may be arbitrarily combined to form a redundant network.

The communication control method according to this embodiment is applicable not only to the configuration example described above but also to any redundant network. Also, the communication protocol is not limited to EtherCAT, and can be applied to any communication protocol that sequentially transfers data such as frames or packets.

<H. Note>
The present embodiment as described above includes the following technical ideas.

[Configuration 1]
It comprises a communication unit (112) connected to a network configured so that frames make a round trip, at least a part of the route of the network is redundant, and one or more devices (200, 300) are connected to the network. ) is connected and
a collection unit (50; 1122) for collecting statistical information (160) about frames transmitted through the network;
a connection management unit (60) that logically disconnects the section between the two devices by sending a command to the two devices;
A communication device, comprising: an identification unit (70) that identifies a section in which a fault occurs based on a change in the statistical information when the section included in the network is logically disconnected.

[Configuration 2]
The communication device according to configuration 1, wherein the connection management unit maintains a state in which the faulty section is separated from the network.

[Configuration 3]
3. The communication device according to configuration 1 or 2, wherein the connection management unit isolates the faulty section from the network in accordance with a user's operation.

[Configuration 4]
The communication according to any one of configurations 1 to 3, wherein the statistical information includes an error rate indicating a ratio of the number of lost frames and error-generated frames to the number of frames transmitted from the communication device. Device.

[Configuration 5]
The communication device according to configuration 4, wherein the identifying unit determines the possibility of the faulty section based on the degree of suppression of the error rate for each logically connected section.

[Configuration 6]
The communication device according to any one of configurations 1 to 5, wherein the specifying unit starts a process of specifying the faulty section when the statistical information satisfies a predetermined condition. .

[Configuration 7]
The connection management unit sequentially selects two adjacent devices, transmits a port closing command to the selected two devices, and then a port opening command to the selected two devices. 7. The communication device according to any one of configurations 1 to 6, which transmits the

[Configuration 8]
8. The communication device according to any one of configurations 1 to 7, further comprising a notification unit for notifying the section in which the failure has occurred to the outside.

[Configuration 9]
A communication control method executed by a communication device (100) connected to a network configured so as to make one round of frames, wherein at least a part of the route of the network is made redundant, and the network has one Or a plurality of devices (200; 300) are connected, and the communication control method is
collecting statistical information about frames transmitted over the network (S2, S12);
a step of logically disconnecting the section between the two devices by sending a command to the two devices (S8, S10);
A communication control method comprising steps (S14, S16) of identifying a section in which a fault occurs based on a change in the statistical information when the section included in the network is logically disconnected.

[Configuration 10]
A communication control program (1102) executed by a computer (100) connected to a network configured to make one round of frames, wherein at least a part of a route of the network is made redundant, and the network includes: is connected to one or more devices (200; 300), and the communication control program is provided to the computer,
collecting statistical information about frames transmitted over the network (S2, S12);
a step of logically disconnecting the section between the two devices by sending a command to the two devices (S8, S10);
A communication control program for executing steps (S14, S16) of identifying a section in which a fault occurs based on a change in the statistical information when the section included in the network is logically disconnected.

<I. Advantage>
The communication system according to the present embodiment can reliably determine whether or not a failure has occurred in each section included in the network. etc. By performing such fault identification and isolation functions, stability can be maintained in a redundant network.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1 communication system, 20, 21, 22, 23, 24, 25, 26 cable, 50 collection module, 60 connection management module, 70 identification module, 100 PLC, 102, 202, 302, 402 processor, 104, 204, 304, 404 main memory, 110, 210, 310, 410 storage, 112, 212 field network controller, 114 local bus controller, 116 functional unit, 118, 228 internal bus, 151, 152 port, 160 statistical information, 200 functional device, 206, 306 control circuit, 220 function module, 251, 351 first port, 252, 352 second port, 300 relay device, 312 field network interface, 353 third port, 400 support device, 406 input section, 408 display section, 412 communication controller, 416 optical drive, 418 storage medium, 424 USB controller, 450,470 user interface screen, 452 network diagram, 454 highlight, 456 separated mark, 458 dialog, 460 cursor, 462 contribution rate, 1102 system program, 1104 User Program, 1122 Network Management Module, 4102 OS, 4104 Development Program.

Claims (10)

comprising a communication unit connected to a network configured so that frames circulate, at least a part of the route of the network being redundant, and one or more devices being connected to the network;
a collection unit for collecting statistical information about frames transmitted through the network;
a connection management unit that logically disconnects a section between the two devices by sending a command to the two devices;
and an identifying unit that identifies a section in which a fault occurs based on a change in the statistical information when the section included in the network is logically disconnected. 2. The communication device according to claim 1, wherein said connection management unit maintains a state in which said faulty section is separated from said network. 3. The communication device according to claim 1, wherein said connection manager isolates said faulty section from said network in accordance with a user's operation. 4. The statistical information according to any one of claims 1 to 3, wherein the statistical information includes an error rate indicating a ratio of the number of lost frames and error-generated frames to the number of frames transmitted from the communication device. Communication device. 5. The communication device according to claim 4, wherein the identifying unit determines the possibility of the faulty section based on the degree to which the error rate is suppressed for each logically connected section. . 6. The communication according to any one of claims 1 to 5, wherein said identifying unit starts a process of identifying said faulty section when said statistical information satisfies a predetermined condition. Device. The connection management unit sequentially selects two adjacent devices, transmits a port closing command to the selected two devices, and then a port opening command to the selected two devices. The communication device according to any one of claims 1 to 6, which transmits the The communication device according to any one of claims 1 to 7, further comprising a notification unit for notifying the section in which the failure has occurred to the outside. A communication control method executed by a communication device connected to a network configured so that frames circulate, wherein at least a part of a route of the network is made redundant, and the network has one or more A device is connected, and the communication control method includes:
collecting statistical information about frames transmitted through the network;
sending a command to two devices to logically disconnect the interval between the two devices;
and identifying a section in which a failure occurs based on a change in the statistical information when the section included in the network is logically disconnected. A communication control program executed by a computer connected to a network configured to allow frames to circulate, wherein at least a part of the route of the network is redundant, and one or more devices are connected to the network. is connected, and the communication control program is connected to the computer,
collecting statistical information about frames transmitted through the network;
sending a command to two devices to logically disconnect the interval between the two devices;
and identifying a section in which a fault has occurred based on a change in the statistical information when the section included in the network is logically disconnected.

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